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1980 (2)
1Author    ErichF. Elstner, W. OsswaldRequires cookie*
 Title    Chlorophyll Photobleaching and Ethane Production in Dichlorophenyldimethylurea-(DCMU) or Paraquat-Treated Euglena gracilis Cells  
 Abstract    Light dependent (35 Klux) chlorophyll bleaching in autotrophically grown Euglena gracilis cells at slightly acidic pH (6.5 —5.4) is stimulated by the photosystem II blockers DCMU and DBMIB (both 10~5 m) as well as by the autooxidizable photosystem I electron acceptor, paraquat (1 0 -3 m). Chlorophyll photobleaching is accompanied by the formation o f thiobarbituric acid — sensitive material ("malondialdehyde") and ethane. Both chlorophyll photobleaching and light dependent ethane formation are partially prevented by higher concentrations (10~* m) o f the autooxidizable photosystem II electron acceptor DBMIB or by sodium bicarbonate (25 m M). In vitro studies with cell free extracts (homogenates) from E. gracilis suggest that a-linolenic acid oxidation by excited (reaction center II) chlorophyll represents the driving force for both ethane formation and chlorophyll bleaching. Ethane formation thus appears to be a sensitive and non-destructive "in vivo'' marker for both restricted energy dissipation in photosystem II and, conditions yielding reactive oxygen species at the reducing side o f photosystem I. 
  Reference    Z. Naturforsch. 35c, 129—135 (1980); received August 20/September 28 1979 
  Published    1980 
  Keywords    Chlorophyll Bleaching, Herbicides, Euglena gracilis, Ethane, Fat Oxidation 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0129.pdf 
 Identifier    ZNC-1980-35c-0129 
 Volume    35 
2Author    E. F. Elstner, E. Lengfelder, G. KwiatkowskiRequires cookie*
 Title    Paraquat-Catalyzed Photodestructions in Subchloroplast Particles are Independent on Photosynthetic Electron Transport  
 Abstract    Light dependent ethane form ation and chlorophyll bleaching in isolated chloroplast lamellae are enhanced by either methylviologen or a-linolenic acid. Both ethane formation and chloro­ phyll bleaching are also enhanced in chloroplast particles deficient in photosynthetic electron transport, e. g. after aging, heat treatm ent or digitonin fragmentation. Ethane form ation by sub­ chloroplast particles from endogenous substrates in the presence of methylviologen is inhibited by superoxide dism utase or by a penicillam ine copper complex exhibiting superoxide dismutase activity whereas chlorophyll bleaching is enhanced by superoxide dismutase — active substances. Maximal rates o f ethane form ation in subchloroplast particles are observed when more than 50% of the chlorophyll is bleached and continues after 98% chlorophyll bleaching. This result indi­ cated that methylviologen -stim ulated ethane production in subchloroplast particles is not de­ pendent on photosynthetic electron transport but involves "activated oxygen" — species like the superoxide radical ion, generated by a light receptor derived from the pigmentsystem o f photo­ system I or activated after its destruction. 
  Reference    Z. Naturforsch. 35c, 303—307 (1980); received D ecem ber 12 1979 
  Published    1980 
  Keywords    Ethane Form ation, Chlorophyll Bleaching, Oxygen Radicals, Fatty Acid Peroxidation 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0303.pdf 
 Identifier    ZNC-1980-35c-0303 
 Volume    35